Abstract: This study examines the use of a modified form of the Theory of Planned Behavior in understanding the decisions of undergraduate students in engineering and humanities to engage in cheating. We surveyed 527 randomly selected students from three academic institutions. Results supported the use of the model in predicting ethical decision-making regarding cheating. In particular, the model demonstrated how certain variables (gender, discipline, high school cheating, education level, international student status, participation in Greek organizations or other clubs) and moral constructs related to intention to cheat, attitudes toward cheating, perceptions of norms with respect to cheating, and ultimately, cheating behaviors. Further the relative importance of the Theory of Planned Behavior constructs was consistent regardless of context, whereas the contributions of variables included in the study that were outside the theory varied by context. Of particular note were findings suggesting that the extent of cheating in high school was a strong predictor of cheating in college and that engineering students reported cheating more frequently than students in the humanities, even when controlling for the number of opportunities to do so.